At XKs Unlimited we rebuild just about every Jaguar mechanical component ourselves, from engines and transmissions to differentials and complete I.R.S. units. We have the knowledge, experience, and spare parts required to complete these tasks efficiently and to the highest standards. Our depth of understanding allows us to make prudent improvements and upgrades to your specifications as well.
Our in-house machine shop handles all phases of cylinder head rebuilding; we replace and machine valve seats, install valve guides and repair corrosion. All heads are painted and polished to original specifications and are returned with cams installed, valves adjusted and ready to run.
Repair shops capable of rebuilding a Jaguar engine are disappearing at a rapid rate. Not that the remaining shops aren’t good – some are excellent, but when a non-specialist takes on a Jaguar engine there is an inevitable learning curve. That’s why a valuable vintage engine should only be entrusted to a specialist such as XKs Unlimited.
The foundation of a successful rebuild starts with the machine work, such as boring the block, turning the crankshaft, rebuilding the connecting rods and the finicky process of restoring the valve train. At XKs Unlimited we not only crack-check the block and head, but they’re also sonic-checked to verify water-jacket thickness and ensure problem areas such as the exhaust port “floors” are not corroded beyond repair. Crankshafts are re-nitrided to restore the surface hardness of the bearing journals and ensure long crankshaft life. Piston rings are hand-fitted to maintain proper end gaps and all rotating components are balanced. The valve train presents its own challenges; critical dimensions such as valve-seat depth, valve-stem height and tappet-to-guide clearance must all be correct if the engine is to sound like a Jaguar and not a farm implement.
Nothing is left to chance. Different technicians perform the machine work and assembly, for instance, so all critical dimensions are double-checked. We verify the valve-to-piston clearance on every engine because past machine work can significantly alter this measurement (sometimes with disastrous results). We use only ARP-brand rod nuts and bolts, which are significantly stronger than original parts, and use our own chrome-moly valve spring retainers.
We see very few engines that have not been rebuilt at least once (and we use the term “rebuilt” loosely). Miss-matched parts are not uncommon. An inexperienced technician, for instance, would not have recognized the XJ-6 oil filter housing installed on an XK engine we recently rebuilt. It fit fine, but the oil pressure relief valve was incorrect and would have resulted in far too much oil pressure.
For a nominal fee, we can run and heat-cycle your engine on a test stand. The trial’s value was recently demonstrated when we found a leaking V-12 core plug. It was easily replaced, which would not have been the case had the engine been installed in the chassis.